This invention pertains to the art of oil extraction from a vegetable oil bearing material such as canola, corn germ, rapeseed, and the like, and more particularly, to a method and assembly for pre-treating oil bearing vegetable material, extracting the oil therefrom, and producing a high quality vegetable oil suitable for physical refining. This invention also pertains to the art of producing a substantially toxic-free meal from oil-bearing materials according to the process of this invention.
The invention is particularly applicable to the processing of oil from canola and corn germ, but is also applicable to many other vegetable oil bearing materials such as rapeseed, cotton seed, peanuts, sunflower seed, grape seed, fresh coconut meat, dried coconut meat, palm fruit, palm kernels and the like.
Conventional vegetable oil extraction processes produce crude oil. As the name implies the product is crude, i.e., it is laden with impurities, solid residues and sometimes water and micro-organisms. The impurities usually include free fatty acids; phospholipids; unsaponifiable matter such as plant sterols, tocopherols and hydrocarbons; trace metals; waxes; minerals and various organic complexes which may cause an undesirable "color" or "pigmentation" of the oil. Of course, some of the "impurities", such as some of the tocopherols, may be desirable. The solid residues can be cell fragments and other non-oil constituents from the oil seeds and agglomerates of phospholipids. All these impurities and solid residues cause a typical crude oil to be a foul smelling, dark appearing, sludge laden and ill tasting liquid which is indeed unfit for human consumption. It is desirable to refine these crude oils to render them fit for human consumption, and to impart the qualities of light color, bland taste and lack of odor that are often preferred.
Some of the impurities in the solid product are toxic. It is thus desirable to obtain a solid product that is non-toxic.
The Strop et al.--U.S. Pat. No. 4,808,426, incorporated herein by reference, discloses a process for extracting oil from oil-bearing materials such as soybean, corn and the like, in order to produce a vegetable oil that is physically refinable without any further pretreatments. The process comprises adding at least one reagent for reducing the phospholipid content in the oil extracted, as well as an oil of preferably the same type as will be extracted, to the oil bearing material to form a slurry mixture. The oil bearing material generally comprises oil seeds or comminuted oil seeds. When the reagent and oil are added to the oil bearing material, a flowable slurry is created. In addition, a medium for a beneficent reaction which purifies the oil produced is also created. The slurry is heated at a preselected temperature for a preselected period of time, and preferably under partial vacuum. Such heating takes place in a grinding mill and slurry preparation tank.
Further processing reduces the phospholipid and trace metal content in the oil extracted from the oil bearing material. The oil product produced is light in color, shows no turbidity, and exhibits a minimal amount of phosphorous, calcium, magnesium and iron. Such product oil is ready for physical refining.
When the process set forth in U.S. Pat. No. 4,808,426 is in continued operation, a major fraction of the oil from the solid-liquid separation steps is returned to the process to be mixed with the oilseeds or comminuted oilseeds. The composition of the oil is substantially that of the oil intrinsic in the oil seeds, except, as stated above, the beneficent reactions set forth in the patent have purified the oil to a major extent.
When a vegetable oil mill using the process of U.S. Pat. No. 4,808,426 is first started up, a charge of oil from an extraneous source is needed, i.e., from a source other than the very seeds to be fed to the process at the initiation of the start up. This source must be extraneous because at the time of the start up, no oil has yet been produced from the seeds to be used. It is convenient to use an oil produced in earlier production runs for the start-up. If desired or available, a fully refined oil, i.e., an oil low in phospholipids, very low in free fatty acids, light in color and low in moisture may be used. Similarly, a partially refined oil, a chemically or physically treated oil, or an oil which has been chemically changed in composition (such as, for example, a hydrogenated oil) may also be used to initially charge the process. Each of these variations of the initial oil charge used is adaptable to the disclosure in U.S. Pat. No. 4,808,426.
During start up and operation of the process, it is foreseeable to use oils which contain additives, other than the reagents claimed in the patent, for converting the product oil into a physically refinable oil.
Once the process of the patent is in operation, a start-up oil is no longer needed because a large portion of the refined oil can be or is recycled back to the early stages of the process. The recycled oil provides a carrier medium for continued process operation.
The grinding mill or slurry preparation tank receives ingredients including seeds, reagents, water and oil. These ingredients are simultaneously stirred and reacted or cooked, and then fed to an evaporator. In large extraction mills, the tank is rather large in size. Both optimization of control of the beneficial physical and chemical processes promoting the sequestration of impurities, such as the phospholipids, and the subsequent extraction of the oil from the oil seeds, become difficult as a result of large tank size.
Large tanks are often not ideal as "reactors" for handling temperature sensitive materials at moderate temperatures. This is because it becomes prohibitively difficult to exclude oxygen, and hence expensive. In many cases, a small, highly stirred, high temperature reactor would be preferred, because the high temperatures accelerate all of the beneficial processes, while the short hold-up time in such a small reactor would prevent undesirable processes and reactions from taking place. In addition, sealing, i.e., preventing air and thus oxygen from entering such a reactor, is easier when the reactor is small.
Although the process set forth in U.S. Pat. No. 4,808,426 patent has provided substantial commercial success, it would be desirable to alter the process to provide a source of oil which could act as a start-up as well as a continuous carrier medium.
It would be further desirable to utilize a preexisting oil prepressing plant in an early step in a process directed to preparing physically refinable oil.
It would be further desirable to provide a process for extracting and refining oil from oil bearing seeds, an initial step of the process taking place in a compact, continuous reactor.
It would be further desirable to treat the oilseeds so as to provide oilseeds having increased porosity and extractability.
It would be further desirable to obtain a toxic-free meal from oil bearing materials in accordance with the process of this invention.
The present invention contemplates a new and improved process which overcomes all of the above-referenced problems and others, and provides a more efficient processing of a better quality, physically refinable oil product from a vegetable oil material as well as a substantially toxic-free meal.